.Viola×bissellii is
a fertile hybrid between V. sororia and V. cucullata.
It is prolific and widespread, especially common in
areas disturbed by humans. Specimens exhibit a wide range of
intermediate character states, including degree and location of
pubescence, length and shape of petal ("beard") hairs, number of cilia on the
sepals, and height of peduncles, which
may overtop leaves. Beard
hairs are often from 0.5-0.9 mm in length and slightly expanded apically
(i.e., intermediate between the corresponding traits of the parents).

". . . a sparsely
pubescent, robust plant with sparsely ciliate sepals (at least on the
auricles), slightly expanded petal hairs (i.e., intermediate between the
two parents), variably prostrate to ascending cleistogamous peduncles,
and a spurred petal that sometimes shows a few hairs. The corolla of
this hybrid can be largely blue or is sometimes largely white with a
blue ring around the white center."

We can suspect that
plants matching the above description, especially where flowers are held
above the height of the leaves, could be V. ×bissellii.